This invention relates to belt conveyors and, more particularly, to an assembly for loading material onto the central area of a conveyor belt under conditions where the conveyor belt shifts from its predetermined centered position along the conveyor frame and relative to the head and tail pulleys of the conveyor.
A belt conveyor for transporting aggregate material is generally a trough-type conveyor which may be loaded at the tail section of the conveyor by another conveyor, or in mining operations, by a mining machine. The conveyor may also be loaded at any point along its length by another conveyor or by itself in those instances where the belt is stepped to a lower position by forming an "S" curve. Belt conveyors are provided with edge aprons which direct the material being loaded to the central portion of the conveyor belt. Under ideal conditions, these conveyors perform their intended functions. However, conditions are seldom ideal, particularly in coal mining operations where belt sections are removed or replaced to shorten or lengthen the conveyor or belt sections are spliced if the belt should break. Spliced belt joints tend to displace the belt as the splice travels along the idler rollers, and as a result, the belt tends to shift laterally from its centered position. This lateral shifting is frequently sufficient to expose the idler pulleys or the drive pulleys, and the material being loaded will miss the conveyor belt and foul mechanisms in the conveyor. The presence of coal or rock in the moving mechanisms frequently causes expensive breakage and disastrous down time.
In view of the above problems, attempts have been made to restrict belt shifting by mechanical constraints or by rollers which are skewed or steered to induce the belt to return to a centered position. Mechanical restraint of the belt is largely ineffective since frictional and inertial forces of the belt are extremely difficult to resist. Mechanical stops, therefore, tend to either tear up the belt or be damaged themselves. Skewing or canting rolls are expensive and must be hydraulically or mechanically linked to electronic edge sensing guides, and such sensitive equipment does not have a long life in a hostile environment, such as a mine.